In higher plants the female germline is formed from the megaspore mother cell (MMC), a single cell in the pre-meiotic ovule. Previously, it was reported that mutants in RNA dependent DNA methylation - RdDM - pathway might be involved in restricting female germline to a single nucellus cell. We show that the DRM methyltransferase double mutant drm1drm2 also presents also presents ectopic enlarged cells, consistent with supernumerary MMC-like cells. In wild-type ovules MMC differentiation required SPOROCYTELESS/NOZZLE (SPL/NZZ), as demonstrated by the spl/nzz mutant failing to develop an MMC. We address the poorly understood upstream regulation of SPL/NZZ in ovules, showing that the RdDM pathway is important to restrict SPL/NZZ expression. In ago9, rdr6 and drm1drm2 mutants, SPL/NZZ is ectopically expressed, suggesting that the mutiple MMC-like cells observed might be due to the ectopic expression of SPL/NZZ. We show that the ovule identity gene SEEDSTICK, directly regulates the AGO9 and RDR6 expression in the ovule and therefore indirectly SPL/NZZ expression. A model is presented describing the network required to restrict SPL/NZZ expression to specify a single MMC.

Fruits are an important source of vitamins, minerals and nutrients in the human diet. They also contain several compounds of nutraceutical importance that have significant antioxidant and anti-inflammatory roles, which can protect the consumer from diseases, such as cancer, and cardiovascular disease as well as having roles in reducing the build-up of LDL-cholesterol in blood plasma and generally reduce the risks of disease and age-related decline in health. Cherries contain high concentrations of bioactive compounds and minerals, including calcium, phosphorous, potassium and magnesium, and it is, therefore, unsurprising that cherry consumption has a positive impact on health. This review highlights the development of sweet cherry fruit, the health benefits of cherry consumption, and the options for increasing consumer acceptance and consumption.

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Main conclusion This manuscript identifies cherry orthologues of genes implicated in the development of pericarpic fruit and pinpoints potential options and restrictions in the use of these targets for commercial exploitation of parthenocarpic cherry fruit. Abstract Cherry fruit contain a large stone and seed, making processing of the fruit laborious and consumption by the consumer challenging, inconvenient to eat ‘on the move’ and potentially dangerous for children. Availability of fruit lacking the stone and seed would be potentially transformative for the cherry industry, since such fruit would be easier to process and would increase consumer demand because of the potential reduction in costs. This review will explore the background of seedless fruit, in the context of the ambition to produce the first seedless cherry, carry out an in-depth analysis of the current literature around parthenocarpy in fruit, and discuss the available technology and potential for producing seedless cherry fruit as an ‘ultimate snacking product’ for the twenty-first century.